<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
    Object.prototype.a="a";
    var obj={
        name:undefined
    }
    console.log("a" in obj)
    console.log(obj.hasOwnProperty("a"))  // js中的方法都是浅不变形的 他们全部都不会上原型链

    console.log(Object.getOwnPropertyNames(obj))
</script>
</html>